Bob You can do it with a SQL query in MapInfo, but it may be best first to change the table structure and add an extra column - eg, EXCLUDE - as a Boolean (is that right? I don't have MI up to check its data types). You can then put a "True" or "yes" value into those you want to exclude, the others will default to "False". The first thing is to find all points with a duplicate (ie, exactly the same) northing and easting, and decide which of them you want to exclude. Once that is done, a new query to select those where EXCLUDE = False gets you the final set of points that you need for plotting. If all of your data is in MS Access it's a little easier to change the table structure, query for duplicates, and browse all of them in order to flag the ones you DON'T want. Then, the second query is very simple in MapInfo.
Ian Thomas -----Original Message----- From: Bob Hudson [mailto:[EMAIL PROTECTED] Sent: Saturday, 27 March 2004 2:49 PM To: [EMAIL PROTECTED] Subject: MI-L How to ignore duplicate points in the same file? I have a database of 50,000 or so villages and towns in Burma. Quite a few have two or more names, and the database copes with this by putting two or more points on the same spot, each with a different name. I am trying to do nearest neighbour analysis on clusters of sites, using two copies of a file of selected data. But if I select villages within a certain area, I get a lot of duplicates, resulting in a statistically unviable neighbour to neighbour value of 0 for each duplicated site. I guess one possibility is to select my sites within the required area, then manually create a single new point on each one in a new layer, just for the purposes of NN measurement, but is there a less time-consuming way to do it? The database, by the way, is from the US Geonet names server, a wonderful free resource, and God bless those American taxpayers who have provided it :-) http://earth-info.nga.mil/gns/html/cntry_files.html Bob Hudson Archaeology Department, University of Sydney, Australia. http://acl.arts.usyd.edu.au/~hudson/bobhpage.htm Using MI 7, Win XP Pro --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 11138 --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 11139
